The development of high speed communications protocols, and the hardware to implement these protocols, brought about the capability for numerous computers to communicate with one another over a so-called local area network (LAN). Presently, many organizations have LANs, which allow the organization's employees to communicate with one another, and collaborate on various projects, each from their own computer workstation. One drawback of LANs, at least until recent years, was that LAN access was limited to a physical hardware infrastructure. In other words, users could only connect to a LAN node through some physical hardware, be it a network cable or a telephone land line.
More recently, wireless LAN technology was developed to overcome at least some of the drawbacks of physical connectivity of wired LANs. A wireless LAN can either replace or extend a wired LAN. In a wireless LAN data may be transmitted and received via radio frequency (RF) waves. Specifically, to transmit data from one wireless LAN node to another, data modulates an RF carrier wave, which the node then transmits to one or more receiving nodes. The receiving nodes may then demodulate the data from the transmitted carrier wave.
In order to provide consistency for wireless LAN data transmission, a standard was developed by the Institute of Electrical and Electronics Engineers (IEEE). The standard, known as IEEE 802.11, provides a specification for over-the-air interface between nodes in a wireless LAN. The IEEE 802.11 standard includes several specifications and provides for data transmission rates from 1 Megabits per second (Mbps) up to 54 Mbps, depending on the frequency of the carrier wave and the transmission paradigm employed. For example, IEEE 802.11(a) provides up to 54 Mbps using a 5.8 GHz carrier wave and an orthogonal frequency division multiplexing encoding scheme, and IEEE 802.11(b) provides up to 11 Mbps using a 2.4 GHz carrier wave and direct sequence spread spectrum (DSSS) transmission.
Presently, many wireless LAN transmitters include integrated circuits (ICs) that are designed to implement both the IEEE 802.11(a) and 802.11(b) standards. Thus, these ICs may have two output ports, one for 2.4 GHz and one for 5.8 GHz. In addition, these ICs may employ two separate power amplifiers, one for each of these carrier frequencies. Alternatively, if a single power amplifier is provided, then the IC may include switching circuitry to reconfigure the IC for operation at the different frequencies. In either case, providing additional circuitry can increase circuit design complexity and cost, as well as IC manufacturing costs.
Hence, there is a need for a circuit that can be used to implement both the IEEE 802.11(a) and (b) standards that does not rely on two power amplifiers or on potentially complex switching circuitry. The present invention addresses these needs.